This application claims the benefit under 35 U.S.C. 119(a) of Korean Patent Application No. 10-2004-0034270, filed on May 14, 2004, the entire disclosure of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a tension adjuster for a belt of an image forming apparatus. More particularly, the present invention relates to a tension adjuster for a belt for printing which produces tension on the belt only when the belt is in operation.
2. Description of the Related Art
In general, an electrophotographic printer such as a laser printer prints an image by forming an electrostatic latent image on a photosensitive medium. The electrophotographic printer develops the electrostatic latent image using a toner having a predetermined color. Then, the electrophotographic printer transfers the developed image to a sheet of print paper.
FIG. 1 illustrates a portion of a conventional image forming apparatus using a photosensitive belt as a photosensitive medium. Referring to FIG. 1, the image forming apparatus includes a photosensitive belt 10 supported by a plurality of rollers 11, 12, 13, and 14. The photosensitive belt 10 circulates along an enclosed path on which a charger 15, a laser scanning unit (LSU) 16, and a developer 17 are disposed.
The charger 15 charges the photosensitive belt 10 to a predetermined potential. The LSU 16 scans light onto a surface of the charged photoreceptor belt 16 to form an electrostatic latent image and the developer 17 develops the electrostatic latent image into a toner image. A transferring roller 20 rotates in contact with the photosensitive belt 10 and transfers the toner image to a printing medium P passing therebetween.
The roller 11 is a driving roller which drives the photosensitive belt 10. Tension roller 14 applies an appropriate tension to the photosensitive belt 10. The rollers 12 and 13 have respective shafts supported at fixed positions. A shaft 14a of the tension roller 14 is connected to a shaft 42 by a pair of swing arms 30. The tension roller 14 is supported by the shaft 42 and is disposed a predetermined distance from the shaft 14a. The shaft 14a is elastically biased in a direction A to produce a tension on the photosensitive belt 10.
FIG. 2 illustrates an enlarged view of the tension adjuster illustrated in FIG. 1. Referring to FIG. 2, the swing arms 30 connect shafts 14a and 42. A tension spring 44 and a boss 46 are disposed on the shaft 42 adjacent to one of the swing arms 30. The boss 46 is fixed to the shaft 42. One end of the tension spring 44 is connected to the boss 46. The other end of the tension spring 44 is connected to the swing arm 30 in an elastically biased state. The tension spring 44 forces the swing arms 30 to elastically bias toward the photosensitive belt 10 (in the direction A in FIG. 1). Therefore, the tension roller 14 maintains tension on the photosensitive belt 10.
The conventional tension adjuster produces a tension on the photosensitive belt 10 regardless of whether the photosensitive belt 10 is being used. Therefore, when a printer is not used for a long period of time, the photosensitive belt 10 becomes deformed, thereby degrading print quality.
In Japanese Patent Publication No. 2001-22188, the entire disclosure of which is hereby incorporated by reference, an apparatus is disclosed to prevent the deformation of a photosensitive belt. The apparatus includes a cam and a plurality of gears that transmit the rotation of a driving unit of the photosensitive belt to the cam.
However, the apparatus is relatively complicated since a cam is used. Moreover, a tensile force of the photosensitive belt may change after the photosensitive belt is used for a relatively long period of time.
Accordingly, there is a need for a photosensitive belt for printing having a tension adjuster being capable of effectively maintaining and releasing tension on the photosensitive belt while minimizing size.